Lots of good information in the post by
@Paladin7 .
For the magnum calibers (44 and 357) Lee has the regular FCD, and then they have the collet style crimper. (They won't work on 44spl or 38spl). I highly recommend the collet crimper. As a bonus, the collet crimpers do not have the carbide rings in them. The collet crimper also does not depend as much on all the cases being trimmed to the same length.
Some people despise the LEE FCD, others love them. Generally, I like them, but the 44 caliber FCD has a carbide ring that is too small and swages some of the bullets, so I don't use it. Some of my bullets are .431" so that is part of the problem, and if you want to use cast bullets, this will likely be a problem. And unless the bullet has an actual crimp groove and not just a cannelure, I much prefer crimping in a separate step.
I like having two scales - and a set of check weights or at least a couple of reference weights as
@someguy2800 mentioned. (I write the weight of my scale pans on the bottom, and use that as a sanity check sometimes). The second scale could be another digital, or a balance beam. Counting my Chargemaster, I have three digital scales and a nice balance beam - I hardly use the balance beam anymore. The tare feature on digitals make them much more handy for the way I work, but that is just me.
I, too, started with a Dillon 550. I am mechanically inclined and definitely an engineering type, so it was relatively easy for me to get setup and started with the 550. I also had a mentor that used a 550, so that helped. But I eventually ended up with a couple of single stage presses and then the LCT, and I find myself using the LCT more than the 550. I decap all my brass on the LCT using a universal decapping die, and one of the reasons I picked the LCT was because of the way it handles spent primers - they fall through the ram and out of the bottom, keeping the primer residue and range dirt from gumming up the ram. And by not doing the decapping on my 550, it stays MUCH cleaner as a result. Most people I know with a progressive press also have a turret or single-stage press that they use for utility purposes, such as decapping or bullet pulling with a collet puller, so why not start there and then decide if a progressive if necessary. You will not have wasted any time or money.